CyberKnife for Melanoma

Because of its range and flexibility, the CyberKnife® radiosurgery platform is ideally suited to match the wide variety of melanoma presentations, effectively treating localized melanoma lesions throughout the body, with radiosurgical precision.

Brain Metastasis

Radiosurgery has been extensively applied against melanoma metastatic to the brain, producing a far better response rate than conventional radiotherapy, including a small percentage of patients with responses lasting greater than 4 years, similar to the result reported by surgical resection plus post-operative whole brain radiotherapy (9,17). Smaller lesions respond more favorably than larger lesions (18,19,20) versus 42% for lesions larger than 2 cm (18). The volume of intracranial metastatic disease appears more significant in predicting response to radiosurgery than does the number of individual metastatic lesions (20).

Although the control of individual or even multiple brain lesions with radiosurgery is encouraging, the major challenge remains control of the entire brain, with a total brain recurrence rate of 86% reported in the M.D. Anderson Hospital series at one year, in spite of high local control rates for individual lesions (18). A possible solution to this problem is the planned combination of radiosurgery with whole brain radiotherapy, though the benefit of added whole brain radiotherapy added to radiosurgery has not been clearly established for metastatic melanoma (18).

Unresectable head and neck melanoma lesions

Melanomas arising in locations such as the nose or sinuses are not always easily resectable. Although high dose conventional radiotherapy has successfully controlled some of these lesions, there are many critical normal tissues surrounding these lesions that may limit the ability to give radiation doses potent enough to achieve a high probability of permanent control. CyberKnife® radiosurgery allows a very sharply marginated radiation intensification method, substantially increasing the dose to the melanoma lesion while minimizing the risk of radiation injury to adjacent critical tissues such as the eye, brain and spinal cord.

Uveal melanoma

CyberKnife radiosurgery is capable of producing extremely focal radiosurgery dose patterns and as such, appears to be an appropriate device to use against melanoma lesions that arise in the eye. There are technical hurdles though, such as immobilization of the eye, suggesting that this particular application may be better done through a large academic center with extensive experience in the research and treatment of ocular neoplasms.

Case Study:

Melanoma spine lesions

Melanoma metastatic to the spine frequently recurs after conventional radiation therapy – a situation which has traditionally left only radical spine surgery or uncontrolled pain and neurologic complications as the inevitable outcome. CyberKnife® radiosurgery creates a new paradigm for these patients, providing an impressive 96% response rate for patients with spinal melanoma metastases, the large majority of which have been durable (21).

Lung metastases

The CyberKnife® System is the only radiation method that tracks a moving lung lesion using Synchrony® respiratory tracking, bringing radiosurgical precision to lung lesions. This allows the application of extreme radiation dose escalation to melanoma lung metastases, radiobiologically ablating them in a way that conventional radiation cannot safely match, creating a reasonable alternative to surgical resection.

Conclusion

Early stage melanoma is highly curable with surgery, and in some cases, high dose per fraction superficial radiotherapy (1, 2, 3, 4,5, 6,10). Unfortunately, many melanoma patients present with advanced or metastatic disease that proves recalcitrant to traditional radiotherapy and inaccessible to complete surgical removal (7,8, 9). When radiotherapy is applied, there is evidence that large dose per treatment regimens (hypofractionated radiotherapy) are more effective (13, 14, 15).

Reflecting their unique sensitivity to large dose per fraction radiation treatment, there is evidence that melanoma lesions respond more favorably to radiosurgery than to traditional radiotherapy, as large dose per fraction radiation treatment is exactly what radiosurgery delivers (16,17,18,19,20,21,22,23,24).

CyberKnife® has the distinction of being the only radiation delivery system that brings radiosurgical precision throughout the entire body, causing this device to match very well with the unique tendency of melanoma to produce a wide variety of disseminated, inoperable or recurrent lesions. It gives melanoma patients an additional valuable weapon against their disease.